Cracking dicyclopentadiene to monomer

ABSTRACT

IN THE LIQUID PHASE CRACKING OF DICYCLOPENTADIENE, A PARAFFINIC HYDROCARBON OIL IS EMPLOYED WHICH HAS THE FOLLOWING CHARACTERISTICS: (A) AN INITIAL BOILING POINT OF ABOUT 270* C. TO ABOUT 277* C. (B) A LOW BOILING FRACTION WHEREIN ABOUT 10 TO ABOUT 20% TO THE OIL WILL BOIL OFF WHEN THE TEMPERATURE IS ABOUT 295* TO ABOUT 310* C. (C) A WIDE BOILING FRACTION WHEREIN ABOUT 75% TO ABOUT 85% OF THE OIL BOILS OFF WHEN THE TEMPERATURE IS ABOUT 337* TO ABOUT 357* C.

United States Patent 3,590,089 CRACKING DICYCLOPENTADIENE T0 MONOMERStephen Robota, North Tonawanda, N.Y., assignor to Hooker'ChemicalCorporation, Niagara Falls, N.Y. Filed Oct. 15, 1968, Ser. No. 767,761Int. Cl. C07c 3/26 US. Cl. 260-666 6 Claims ABSTRACT OF THE DISCLOSUREIn the liquid phase cracking of dicyclopentadiene, a parafiinichydrocarbon oil is employed which has the following characteristics:

(a) an initial boiling point of about 270 C. to about (b) a low boilingfraction wherein about 10 to about to the oil will boil off when thetemperature is about 295 to about 310 C.

(c) a wide boiling fraction wherein about 75% to about 85% of the oilboils oil? when the temperature is about 337 to about 357 C.

BACKGROUND OF THE INVENTION The invention relates to the liquid phasecracking of dicyclopentadiene to monocyclopentadiene, and the employmentof a parafiinic hydrocarbon oil as a solvent.

The formation of cyclopentadiene from dicyclopentadiene by means ofhydrocarbon cracking in liquid phase systems is known. There has beendifficulty experienced in the amount of resins which accumulate in thefractionating column and in other pieces of equipment as the cracked gasproceeds from the cracking chamber to the fractionating column. It hasbeen found that the use of a parafiinic hydrocarbon oil with a lowboiling fraction and a wide boiling fraction decreases the resin buildupand facilitates the overall operating system.

In US. Pat. 2,831,904 there is described a liquid phase cracking ofdicyclopentadiene. The improvement described in this patent is the useof an auxiliary liquid, which has a parafiinic hydrocarbon fractionhaving an initial boiling point above 250 degrees centigrade and ofwhich at least 80 percent boils within a range of no greater than about50 degrees centigrade, lying within the range between 250 degreescentigrade and about 350 degrees centigrade, and which permits adecrease in resin buildup and the plugging of mechanical systems.

Another method for cracking cyclopentadiene is the hot tube processwherein dicyclopentadiene is funneled through a heated tube to obtain apure product. An example of such a process is U.S. Pat. 2,582,920.However, the hot tube process is used mainly in the laboratory and isnot readily amenable to commercial operations primarily because ofplugging of the tube after continuous processing.

It is an object of this invention to obtain an improved yield in thecracking of dicyclopentadiene and to obtain a pure product. It is alsoan object to obtain a continuous process for the cracking ofdicyclopentadiene. These and other objects of this invention will becomeevident as the invention is further described below.

*SUMMARY OF THE INVENTION Dicyclopentadiene may be cracked to relativelypure monomer in a paraflinic hydrocarbon oil, which has the followingcharacteristics: (a) an initial boiling point of about 270 to about 277C.; (b) a low boiling fraction wherein about 10 to about 20% to the oilwill boil off when the temperature is about 295 to about 310 C.; (c) awide boiling fraction wherein about 75% to about 3,590,089 Patented June29, 1971 PREFERRED EMBODIMENTS OF THE INVENTION Crude dicyclopentadienemay be employed. However, it is preferred to use relatively puredicyclopentadiene. The resulting monomer from the process of thisinvention is pure monocyclopentadieue. A lower limit of crudedicyclopentadiene would be one that contains approximately percentdicyclopentadiene, with percent purity preferred.

Various paraflinic hydrocarbon oils may be employed as solvents. It ispreferred that the oil not be reactive at the operating temperatures andfurther that it be stable to dicyclo and monocyclopentadiene. Theparaffinic oils that may be employed are those that have the followingcharacteristics: (a) an initial boiling point of about 270 to about 277C.; (b) a low boiling fraction wherein about 10 to about 20% to the oilwill boil off when the temperature is about 295 to about 310 C.; (c) awide boiling fraction wherein about 75 to about 85% of the oil boils offwhen the temperature is about 337 to about 357 C. The characteristics ofan oil can be tested according to ASTM D8661. It is also desirable tohave a paratfinic hydrocarbon oil that will be stable to continuousprocesing. This can be determined by periodically testing the pour pointof the oil as it is recycled. Pour points of about 30 degrees centigradeto about 15 degrees centigrade may be employed. preferably about 20degrees centirgrade to about 10 degrees centigrade.

The cracking temperatures may range from approximately 270 degreescentigrade to about 325 degrees centigrade, preferably 280 degreescentigrade to about 320 degrees centigrade. As the gaseous mixtureleaves the cracking chamber, it enters the partial condenser which maybe maintained at approximately 45 degrees centigrade to about degreescentigrade, preferably approximately 45 degrees to about 70 degreescentigrade. The inlet to the fractionation apparatus should bemaintained at a high enough temperature to keep the monocyclopentadienein the vapor state and low enough to remove the high boiling impurities,such as, dicyclopentadiene or other polymers of cyclopentadiene.

The inlet to the fractionation apparatus may be maintained at about 45degrees centigrade to about 70 degrees centigrade, preferably about 45degrees centigrade to about 65 degrees centigrade. The fractionationapparatus may be maintained at about 40 degrees centigrade.

The cracked gases referred to in this invention are those gases leavingthe cracking chamber. They are generally comprised of cyclopentadiene,hydrocarbon oil and a small amount, if any of dicyclopentadiene. Thefunction of the partial condensor is to condense the hydrocarbon oil,which oil will then run down the inside of the condenser back tothe-cracking chamber. Since the partial condenser is kept relativelycool, high boiling polymers of cyclopentadiene will also be condensedand returned to the cracking chamber.

The cracking chamber for commercial operation may employ a stainlesssteel vessel, a glass lined vessel or some other ceramic vessel.

The partial condenser may be made of carbon steel, a glass lined vesselor other materials obvious to one of skill in the art.

The residence time in the partial condenser should be short about 1 toabout 20 seconds, preferably 1 to about 8 seconds or 5 to about 7seconds and more preferably about 6.6 seconds. Residence times of lessthan about 5 seconds are not preferred for they may require expensiverefrigeration equipment.

The fractionation column is usually packed with ceramic packing whilethe column itself may use glass-lined or nickel walls. The column mayalso be packed with ceramic berl saddles of varying length, such as inchor glass helices of varying lengths such as inch or 1 inch.

In order to obtain improved yields of cyclopentadiene, it is desirablethat the condensed vapors be cooled as quickly as possible.Cyclopentadiene has a tendency to repolymerize which is an exothermicreaction. The purified monocyclopentadiene should be cooled rapidly in azone having a temperature from degrees centigrade to -40 degreescentigrade. The formation of dimer can also be prevented by immediatelyreacting monocyclopentadiene. An example of such a process is describedin Bel- .gium Pat. 498,176 wherein monocyclopentadiene is reacted withacetylene to form bicyclo-(2.2.1)-2,5-heptadiene. Also cyclopentadieneis a highly useful intermediate which can be employed to produce suchcompounds as chlorinated cyclopentadiene, such as chlorendic acid.

This process can be further described by an analysis of the schematicdiagram attached. Dicyclopentadiene from dicyclopentadiene reserve 1directed to the cracking chamber 7 through line 5. The auxiliary liquidis also directed from auxiliary liquid reserve 2 to the cracking chamberthrough line 6. Metering pumps 3 and 4 are employed in order to maintaina constant level of material in the cracking chamber. The materials maybe preheated prior to being added to the cracking chamber. They may alsobe merged together before being added to the cracking chamber. To insurefurther a constant amount of material in the cracking chamber anoverflow vessel 8 is employed. Material from this overflow vessel may bedirected back to the cracking chamber. During the cracking process, theauxiliary liquid will reflux to coat the partial condenser therebypreventing repolymerization of the cyclopentadiene. The gaseous mixturethat leaves the cracking chamber is directed to partial condenser 9wherein it has a short retention time as it continues to thefractionation column 13. In order to cool and condense the gases in thepartial condenser, liquid from cooling liquid reserve 11 pass into thecondenser through line 12 and exit back to the reserve through line 10.The cyclopentadiene gas is directed to the fractionation column 13 fromthe partial condenser and as it exits in the liquid form it can eitherbe stored or passed on for further processing.

The use of a liquid phase cracking system lends itself to the continuousprocess of cracking dicyclopentadiene. As the pure product is removedfrom the auxiliary liquid, said liquid can be recycled and used again.The limiting factors are the amount of resin buildup and the point atwhich the auxiliary liquid becomes clogged with impurities. A quick testfor determining the adequacy of the liquid is by measuring the pourpoint as has been described above.

Varying weight ratios of dicyclopentadiene to paraffinic oil may be usedfrom about 1:1 to 15:1, preferably 4:1 to :1 and even more preferably10:1 (dicyclopentadiene2oil).

From an economic point of view it is preferred to operate the abovedescribed process at atmospheric pressure. To increase product producedper period of time, pressure may be applied. Further during normalprocessing some pressure may buildup in the equipment. It is within thescope of this invention to operate at such minimal pressures.

Parafiinic hydrocarbon oils with the Wider boiling range of theinvention are desirable because less oil will reflux in the partialcondenser thereby preventing clogging and consequently increasing theyields of cyclopentadiene. Further, the oil will be more stable duringthe cracking process and there will be decreased losses of solvent.

Paraffinic hydrocarbon oils with the lower boiling fraction of saidwider boiling range oils are desirable. The function of this low boilingfraction is to boil off and coat the partial condenser. The oil willcontinue to reflux 4 in the condenser, thereby prevent therepolymerization of cyclopentadiene.

The parafiinic hydrocarbon oils of this invention are generally preparedby cracking petroleum. From the cracking of petroleum there are producedseveral fractions. The paraffinic hydrocarbon oils of this invention arethe lighter fractions resulting from the petroleum cracking.

Having described in general the novel points of the invention below areseveral examples indicating preferred operations. These examples are inno way a limitation on the scope of the invention as described above.

EXAMPLE 1 A paraflinic oil having an initial boiling point of about 272degrees centigrade 10 percent of which boiled over at 298 degreescentigrade; 20 percent of which boiled over when the temperature isabout 307 degrees centigrade and percent of which boiled over at about345 degrees centigrade was employed. Charged to a 1000 ml. flask is 400ml. (334 grams) of the oil. The oil was agitated and heated whereby itexpanded to 500 ml. Heated dicyclopentadiene of percent purity was fedto the cracker at various rates up to 3.43 grams per minute. The feed isa dicyclopentadiene oil mixture in a weight ratio of 10 to 1(dicyclozoil). The spent oil was continuously discharged by an overflowline to maintain a 500 ml. oil volume in the cracker. This experimentwas run continuously. Three sample runs are indicated in Table I. Thepercent take off of product is 90 percent.

The dicyclopentadiene feed rate was decreased from 3.43 grams/minute toa low of 1.4 grams per minute to determine if the liquid temperature inthe cracking chamber could be increased. The results indicate that therise in temperature was negligible, reaching 287 degrees centigrademaximum. The pour point of the discharged oil from the cracking chamberremained constant at about ---7 degrees centigrade; the resin buildup inthe partial condenser, in connecting lines and in the fractionatingcolumn was negligible. The overall average product recovery based onfeed was 96.6 percent. The partial condenser volume is about ml.

TABLE I.CRACKING OF DIOYCLOPENTADIENE USING A PARAFFINIC OIL Run No 1 23 Dicyclopentadiene teed:

Grams, as dicyclopentadiene 384 258 463 Grams/minute, asdieyc1opentadiene.- 1. 67 1. 845 1. 685 Cracker liquid volume, ml 500500 500 Cracker vapor volume, ml 500 500 500 Cracker temperatures:

Oil (liquid), average C 280 280 285 (Vapor), Average C 295 286Fractionation system temperature:

Inlet to fractionation column, average, C. 59 60 60 Reflux, average, C40 40 40 Oil discharged from cracker, grams". 80. 0 65. 2 30. 9 Pourpoint of sample, 0. (initial 1 C.) -7 Product collected:

Specific gravity at 20 C 0.8019 0.8017 0. 8014 Percent cyclopentadiene100. 00 100. 0 100. 0 Grams 367. 5 253. 5 450. 1 Recozery(product/feedXlOO), per- 95. 8 97. 5 97. 2

cen Duration of run, minutes 230 140 What is claimed is:

1. A method for cracking dicyclopentadiene to monocyclopentadiene whichcomprises heating dicyclopentadiene in a liquid paraffinic hydrocarbonsolvent having the following characteristics: (a) an initial boilingpoint of about 270 to about 277 C.; (b) a low boiling fraction whereinabout 10 to about 20% to the oil will boil off when the temperature isabout 295 to about 310 C.; (c) a Wide boiling fraction wherein about 75%to about 85% of the oil boils off when the temperature is about 337 toabout 357 C. and recovering the substantially pure monocyclopentadieneby distillation.

2. A method of claim 1 wherein the cracking is performed at atemperature in the range of about 270 to about 325 degrees centigrade.

3. A method of claim 2 wherein the cracking temperature is about 280 toabout 320 degrees centigrade.

4. The method of claim 1 wherein the liquid hydro carbon parafiinicsolvent has an initial boiling point of about 272 to 277 degreescentigrade; 20 percent of which boils over when the temperature is about307 degrees centigrade and 80 percent of which boils over when thetemperature is about 345 degrees centigrade.

5. The method of claim 1 wherein after cracking, the

gaseous mixture is partially condensed at a temperature 10 ReferencesCited UNITED STATES PATENTS 1/1952 Busiuger et a1. 260-666A 4/1958 Kreps260-666A PAUL M. COUGHLAN, 111., Primary Examiner V. OKEEFE, AssistantExaminer

